26-06-2014, 03:02 PM
Automotive Electronics
[attachment=65374]
INTRODUCTION
Automotive Electronics are any electrically-generated systems used in road vehicles, such as: carputers, telematics, in-car entertainment systems, etc...
Automotive Electronics originated from the need to control engines. The first electronic pieces were used to control engine functions and were referred to as Engine Control Units (ECU). As electronic controls began to be used for more automotive applications, the acronym ECU took on the more general meaning of "electronic control unit", and then specific ECUs were developed. Now, ECUs are modular- Engine Control Module (ECM) or Transmission Control Module (TCM).
A modern car may have up to 100 ECUs and a commercial vehicle up to 40.
Automotive electronics or automotive embedded systems are distributed systems, and according to different domains in the automotive field, they can be classified into:
1. Engine electronics
2. Transmission electronics
3. Chassis electronics
4. Active safety
5. Driver assistance
6. Passenger comfort
7. Entertainment systems
1ENGINE ELECTRONICS
One of the most demanding electronic parts of an automobile is the engine control unit. Engine controls demand one of the highest real time deadlines, as the engine itself is a very fast and complex part of the automobile. Of all the electronics in any car the computing power of the engine control unit is the highest, typically a 32-bit processor.
It controls such things as:
In a diesel engine:
• Fuel injection rate
• Emission control, NOx control
• Regeneration of oxidation catalytic converter
• Turbocharger control
• Cooling system control
• Throttle control
In a gasoline engine:
• Lambda control
• OBD (On-Board Diagnostics)
• Cooling system control
• Ignition system control
• Lubrication system control (only a few have electronic control)
TRANSMISSION ELECTRONICS
These control the transmission system, mainly the shifting of the gears for better shift comfort and to lower torque interrupt while shifting. Automatic transmissions use controls for their operation, and also many semi-automatic transmissions having a fully automatic clutch or a semi-auto clutch (declutching only).
The engine control unit and the transmission control exchange messages, sensor signals and control signals for their operation
CHASSIS ELECTRONICS
The chassis system has lot of sub-systems which monitor various parameters and are actively controlled:
• ABS - Anti-lock Braking System
• TCS – Traction Control System
• EBD – Electronic Brake Distribution
• ESP – Electronic Stability Program
FUNCTIONAL SAFETY REQUIREMENTS
In order to minimize the risk of dangerous failures, safety related electronic systems have to be developed following the applicable product liability requirements. Disregard for, or inadequate application of these standards can lead to not only personal injuries, but also severe legal and economic consequences such as product cancellations.
The IEC 61508 standard, generally applicable to electrical/electronic/programmable safety-related products, is only partially adequate for automotive-development requirements. Consequently for the automotive industry, this standard is replaced by the existing ISO 26262, currently released as a Final Draft International Standard (FDIS). ISO/DIS 26262 describes the entire product life-cycle of safety related electrical/electronic systems for road vehicles. It has been published as an international standard in its final version in November 2011. The implementation of this new standard will result in modifications and various innovations in the automobile electronics development process, as it covers the complete product life cycle from the concept phase until its decommissioning.
When developing electric vehicles, it is essential to consider all electrical, chemical, and mechanical safety aspects. The development of safe, high-voltage batteries is regarded as a major challenge. There is still no appendage that addresses safety related aspects of electric propulsion and storage systems. As a result, it is quite a challenge to navigate through the inconsistencies and gaps in the technical standards and legal requirements
ENGINE CONTROL MODULE (ECM)
2.0 ABOUT
The Engine Control Module (ECM) is also known as the Power train Control Module (PCM) or the Engine Control Unit (ECU).
The main responsibility of this controller is to get information from sensors and run certain actuators. In the case of any errors arising the ECU shows a check engine light on your dashboard.
This hub discusses the where and why sensors are placed in certain positions and some insight as to how or what the sensors sense. If you are a DIY person then you could even open up the sensors yourself and clean them for optimum signals to reach your ecu.
2.1.1 ENGINE COOLANT TEMPERATURE SENSOR (ECT)
Like humans, a vehicle needs to maintain a specific temperature in order to function properly. Too cold and the vehicle will drink too much petrol; Too hot and the head gasket could leak. Coolant is a liquid used in the vehicles radiator of the car to maintain a certain temperature at which the engine can perform at its optimum.
The Engine Coolant Temperature Sensor simply tells the car's computer (ECM) the current temperature of the vehicle. When the temperature of the coolant reaches between 75 and 95 degrees (depending on the manufacturer specifications) the ECM instructs the radiator fan to turn on and start cooling down the liquid.
Usually located either on the bottom of the radiator or follow the top radiators hose towards the engine block or you'll see it on mounted on the engine block.
Can be cleaned using a wire brush when you entirely change your engine coolant (approx every 80,000 kms - 50,000 miles)
AIR TEMPERATURE SENSOR (IAT)
The Intake Air Temperature Sensor (IAT) tells the ECM the temperature of the air that is going into the engine. The cooler the air the better the performance of the engine, which is probably why you might have noticed a difference in the cars performance on a summer night as compared to the day.
Usually located on the air filter box or the pipe going from the air filter box to the throttle body. Toyota has a MAF and an IAT sensor built in one unit which has 5 wires located on the air filter box.
Can be cleaned once every 6 months (depending on dust/pollution) using carb cleaner on an ear cleaner
BARO SENSOR / MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP)
The Baro Sensor measures the ambient air pressure which tells the ECM the current altitude of the vehicle. If you're driving in the mountains you'll need less fuel because there is less oxygen in the atmosphere therefore less oxygen in the engine cylinder. The ECM will adjust the fuel injectors "throwing time" or pulse width accordingly.
The map sensor detects the vacuum pressure created inside the intake manifold of the vehicle and sends the engine load information to the ECM. The ECM will adjust the fuel injectors pulse width accordingly.
Note - Baro and MAP Sensors look and work in a similar fashion, therefore only one of the two sensors will be found in one engine.
Usually found either bolted on the intake manifold or linked with a vacuum pipe from the intake manifold.
If mounted on intake manifold then should be cleaned every 6 months to 1 year using crab cleaner. (Depends on fuel quality where you live ... the lower the quality of fuel the more carbon deposits found). I’ve had to clean some every 3 months
IDLE AIR CONTROLLER (IACV)
The IACV is actually an actuator and not a sensor because it does not supply readings to the ECM, but works on the command of the ECM. I just added this actuator for the DIY enthusiast.
There are 2 coolant pipes connected to the housing, which you can see on the far right of the picture shown. The black piece shown in the picture is a magnetic actuator which rotates the valve shaft allowing it to open and close as required by the ECM.
Whenever you start your car the IACV will increase the RPM of the car until the coolant temperature sensor (ECT) tells the ECU that the temperature of the engine is up-to the manufacturer’s specifications. The RPM will then drop down to and remain steady at approx 800rpm. Whenever there is an extra load on the engine the idle controller adjusts and compensates for the load applied. For example switching from park to drive mode in an automatic transmission vehicle, or even when you switch on your air conditioning. You can also adjust the idle speed of the vehicle by loosening the screws on the actuator and rotate the actuator. The default setting of the actuator is normally in the middle.
Located on the throttle body of the vehicle.
Depending on fuel quality, carbon deposits build up and the valve shaft gets stuck resulting in fluctuating RPM signals on the dashboard.
2.1.7CAMSHAFT POSITION SENSOR
The Camshaft position sensor (CMP) is an electro-magnetic sensor which produces a voltage when a metal object moves past it. This sensor is responsible for telling the ECM the current position of the camshaft. With this information the ECM can calculate which valve is open and throw fuel through the injector into that cylinder.
This sensor is found on one end of the camshaft, usually on the right side in a front wheel drive car. it's normally not very difficult to access.
Cleaning can be done with a simple dry cloth but if the oil has been used for too long a golden brown stain is left on metal portion of the sensor. In some cases it even comes out black and goo-ey which is basically old engine oil turned into sludge. if it's stained then you
CRANKSHAFT SENSOR (CKP)
This sensor is very similar to the cam position sensor in functionality. It is responsible for telling the ECM the exact location of the crankshaft as well as the RPM (rotations per minute) of the engine. With this information the ECM knows the position of each piston in each cylinder. Using the cam sensor readings as well as the Crank sensor readings the ECM knows exactly which injector needs to be activated. The synchronization of the cam shaft and the crank shaft in an engine is the key to engine performance. This synchronization is also referred to as the engine timing. With the correct timing you will get the fuel and spark delivered at the right time.
It is located at the bottom of the engine somewhere close to the crankshaft.
Cleaning technique for this sensor is exactly the same as the cam sensor. Cleaning once a year is good enough for this sensor.
Note - if your car does not start a possible reason could be a faulty crank sensor or a broken wire in the crank sensor circuit.
2SYSTEM COMPONENTS
Interior Lighting is controlled through four lighting circuits. Three circuits are BC1 controlled, the fourth, Ashtray Lighting, is controlled via the External Light Switch.
INTERIOR LIGHT SWITCH (ON/OFF MODE)
The interior light switch can be used to turn the interior lights ON and OFF. The interior light switch will operate at all times, except when the alarm is armed. If the interior light switch is used to turn on the interior light, the light stays on for 16 minutes, regardless of the state or change of state of the ignition switch. The interior light will fade off when the vehicle is externally locked, after this the interior light control will be in the "automatic" mode again
TRANSMISSION CONTROL UNIT
ABOUT
A Transmission control unit or TCU is a device that controls modern electronic automatic transmissions. A TCU generally uses sensors from the vehicle as well as data provided by the engine control unit (ECU) to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.
Electronic automatic transmissions have been shifting from purely hydro mechanical controls to electronic controls since the late 1980s. Since then, development has been iterative and today designs exist from several stages of electronic automatic transmission control development. Transmission solenoids are a key component to these control units.
The evolution of the modern automatic transmission and the integration of electronic controls have allowed great progress in recent years. The modern automatic transmission is now able to achieve better fuel economy, reduced engine emissions, greater shift system reliability, improved shift feel, improved shift speed and improved vehicle handling. The immense range of programmability offered by a TCU allows the modern automatic transmission to be used with appropriate transmission characteristics for each application.
On some applications, the TCU and the ECU are combined into a single unit as a power train control module (PCM
INPUT PARAMETERS
The typical modern TCU uses signals from engine sensors, automatic transmission sensors and from other electronic controllers to determine when and how to shift. More modern designs share inputs or obtain information from an input to the ECU, whereas older designs often have their own dedicated inputs and sensors on the engine components. Modern TCUs are so complex in their design and make calculations based on so many parameters that there are an indefinite amount of possible shift behaviours
TRANSMISSION FLUID TEMPERATURE SENSOR (TFT)
This may also be known as Transmission Oil Temperature. This sensor determines the fluid temperature inside the transmission. This is often used for diagnostic purposes to check ATF (Automatic Transmission Fluid) at the correct temperature. The main use of this has been as a failsafe feature to downshift the transmission if the ATF becomes extremely hot. On more modern TCUs this input allows the TCU to modify the line pressure and solenoid pressures according to the changing viscosity of the fluid based on temperature, and also to determine regulation of the torque converter lock-up clutch
KICK DOWN SWITCH
One of the most common inputs into a TCU is the kick down switch which is used to determine if the accelerator pedal has been depressed past full throttle. When activated the transmission downshifts into the lowest permissible gear based on current road speed to use the full power reserves of the engine. This is still present in most transmissions though is no longer as necessary to use as the TCU uses the throttle position sensor and rapid rate of change to determine whether a downshift may be necessary, thus there is no need to use the kick down feature in most circumstances
OUTPUTS TO OTHER CONTROLLERS
The TCU provides information about the health of the transmission, such as clutch wear indicators and shift pressures, and can raise trouble and set the malfunction indicator lamp on the instrument cluster if a serious problem is found. An output to the cruise control module is also often present to deactivate the cruise control if a neutral gear is selected, just like on a manual transmission.
COMPONENTS AND DESIGN
ESC incorporates yaw rate control into the anti-lock braking system (ABS). Yaw is a rotation around the vertical axis; i.e. spinning left or right. Anti-lock brakes enable ESC to brake individual wheels. Many ESC systems also incorporate a traction control system (TCS or ASR), which senses drive-wheel slip under acceleration and individually brakes the slipping wheel or wheels and/or reduces excess engine power until control is regained. However, ESC achieves a different purpose than ABS or Traction Control.
The ESC system uses several sensors to determine what the driver wants (input). Other sensors indicate the actual state of the vehicle (response). The control algorithm compares driver input to vehicle response and decides, when necessary, to apply brakes and/or reduce throttle by the amounts calculated through the state space (set of equations used to model the dynamics of the vehicle). The ESC controller can also receive data from an issue commands to other controllers on the vehicle such as an all wheel drive system or an active suspension system to improve vehicle stability and controllability.
The sensors used for ESC have to send data at all times in order to detect possible defects as soon as possible. They have to be resistant to possible forms of interference (rain, holes in the road, etc.). The most important sensors are:
[attachment=65374]
INTRODUCTION
Automotive Electronics are any electrically-generated systems used in road vehicles, such as: carputers, telematics, in-car entertainment systems, etc...
Automotive Electronics originated from the need to control engines. The first electronic pieces were used to control engine functions and were referred to as Engine Control Units (ECU). As electronic controls began to be used for more automotive applications, the acronym ECU took on the more general meaning of "electronic control unit", and then specific ECUs were developed. Now, ECUs are modular- Engine Control Module (ECM) or Transmission Control Module (TCM).
A modern car may have up to 100 ECUs and a commercial vehicle up to 40.
Automotive electronics or automotive embedded systems are distributed systems, and according to different domains in the automotive field, they can be classified into:
1. Engine electronics
2. Transmission electronics
3. Chassis electronics
4. Active safety
5. Driver assistance
6. Passenger comfort
7. Entertainment systems
1ENGINE ELECTRONICS
One of the most demanding electronic parts of an automobile is the engine control unit. Engine controls demand one of the highest real time deadlines, as the engine itself is a very fast and complex part of the automobile. Of all the electronics in any car the computing power of the engine control unit is the highest, typically a 32-bit processor.
It controls such things as:
In a diesel engine:
• Fuel injection rate
• Emission control, NOx control
• Regeneration of oxidation catalytic converter
• Turbocharger control
• Cooling system control
• Throttle control
In a gasoline engine:
• Lambda control
• OBD (On-Board Diagnostics)
• Cooling system control
• Ignition system control
• Lubrication system control (only a few have electronic control)
TRANSMISSION ELECTRONICS
These control the transmission system, mainly the shifting of the gears for better shift comfort and to lower torque interrupt while shifting. Automatic transmissions use controls for their operation, and also many semi-automatic transmissions having a fully automatic clutch or a semi-auto clutch (declutching only).
The engine control unit and the transmission control exchange messages, sensor signals and control signals for their operation
CHASSIS ELECTRONICS
The chassis system has lot of sub-systems which monitor various parameters and are actively controlled:
• ABS - Anti-lock Braking System
• TCS – Traction Control System
• EBD – Electronic Brake Distribution
• ESP – Electronic Stability Program
FUNCTIONAL SAFETY REQUIREMENTS
In order to minimize the risk of dangerous failures, safety related electronic systems have to be developed following the applicable product liability requirements. Disregard for, or inadequate application of these standards can lead to not only personal injuries, but also severe legal and economic consequences such as product cancellations.
The IEC 61508 standard, generally applicable to electrical/electronic/programmable safety-related products, is only partially adequate for automotive-development requirements. Consequently for the automotive industry, this standard is replaced by the existing ISO 26262, currently released as a Final Draft International Standard (FDIS). ISO/DIS 26262 describes the entire product life-cycle of safety related electrical/electronic systems for road vehicles. It has been published as an international standard in its final version in November 2011. The implementation of this new standard will result in modifications and various innovations in the automobile electronics development process, as it covers the complete product life cycle from the concept phase until its decommissioning.
When developing electric vehicles, it is essential to consider all electrical, chemical, and mechanical safety aspects. The development of safe, high-voltage batteries is regarded as a major challenge. There is still no appendage that addresses safety related aspects of electric propulsion and storage systems. As a result, it is quite a challenge to navigate through the inconsistencies and gaps in the technical standards and legal requirements
ENGINE CONTROL MODULE (ECM)
2.0 ABOUT
The Engine Control Module (ECM) is also known as the Power train Control Module (PCM) or the Engine Control Unit (ECU).
The main responsibility of this controller is to get information from sensors and run certain actuators. In the case of any errors arising the ECU shows a check engine light on your dashboard.
This hub discusses the where and why sensors are placed in certain positions and some insight as to how or what the sensors sense. If you are a DIY person then you could even open up the sensors yourself and clean them for optimum signals to reach your ecu.
2.1.1 ENGINE COOLANT TEMPERATURE SENSOR (ECT)
Like humans, a vehicle needs to maintain a specific temperature in order to function properly. Too cold and the vehicle will drink too much petrol; Too hot and the head gasket could leak. Coolant is a liquid used in the vehicles radiator of the car to maintain a certain temperature at which the engine can perform at its optimum.
The Engine Coolant Temperature Sensor simply tells the car's computer (ECM) the current temperature of the vehicle. When the temperature of the coolant reaches between 75 and 95 degrees (depending on the manufacturer specifications) the ECM instructs the radiator fan to turn on and start cooling down the liquid.
Usually located either on the bottom of the radiator or follow the top radiators hose towards the engine block or you'll see it on mounted on the engine block.
Can be cleaned using a wire brush when you entirely change your engine coolant (approx every 80,000 kms - 50,000 miles)
AIR TEMPERATURE SENSOR (IAT)
The Intake Air Temperature Sensor (IAT) tells the ECM the temperature of the air that is going into the engine. The cooler the air the better the performance of the engine, which is probably why you might have noticed a difference in the cars performance on a summer night as compared to the day.
Usually located on the air filter box or the pipe going from the air filter box to the throttle body. Toyota has a MAF and an IAT sensor built in one unit which has 5 wires located on the air filter box.
Can be cleaned once every 6 months (depending on dust/pollution) using carb cleaner on an ear cleaner
BARO SENSOR / MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP)
The Baro Sensor measures the ambient air pressure which tells the ECM the current altitude of the vehicle. If you're driving in the mountains you'll need less fuel because there is less oxygen in the atmosphere therefore less oxygen in the engine cylinder. The ECM will adjust the fuel injectors "throwing time" or pulse width accordingly.
The map sensor detects the vacuum pressure created inside the intake manifold of the vehicle and sends the engine load information to the ECM. The ECM will adjust the fuel injectors pulse width accordingly.
Note - Baro and MAP Sensors look and work in a similar fashion, therefore only one of the two sensors will be found in one engine.
Usually found either bolted on the intake manifold or linked with a vacuum pipe from the intake manifold.
If mounted on intake manifold then should be cleaned every 6 months to 1 year using crab cleaner. (Depends on fuel quality where you live ... the lower the quality of fuel the more carbon deposits found). I’ve had to clean some every 3 months
IDLE AIR CONTROLLER (IACV)
The IACV is actually an actuator and not a sensor because it does not supply readings to the ECM, but works on the command of the ECM. I just added this actuator for the DIY enthusiast.
There are 2 coolant pipes connected to the housing, which you can see on the far right of the picture shown. The black piece shown in the picture is a magnetic actuator which rotates the valve shaft allowing it to open and close as required by the ECM.
Whenever you start your car the IACV will increase the RPM of the car until the coolant temperature sensor (ECT) tells the ECU that the temperature of the engine is up-to the manufacturer’s specifications. The RPM will then drop down to and remain steady at approx 800rpm. Whenever there is an extra load on the engine the idle controller adjusts and compensates for the load applied. For example switching from park to drive mode in an automatic transmission vehicle, or even when you switch on your air conditioning. You can also adjust the idle speed of the vehicle by loosening the screws on the actuator and rotate the actuator. The default setting of the actuator is normally in the middle.
Located on the throttle body of the vehicle.
Depending on fuel quality, carbon deposits build up and the valve shaft gets stuck resulting in fluctuating RPM signals on the dashboard.
2.1.7CAMSHAFT POSITION SENSOR
The Camshaft position sensor (CMP) is an electro-magnetic sensor which produces a voltage when a metal object moves past it. This sensor is responsible for telling the ECM the current position of the camshaft. With this information the ECM can calculate which valve is open and throw fuel through the injector into that cylinder.
This sensor is found on one end of the camshaft, usually on the right side in a front wheel drive car. it's normally not very difficult to access.
Cleaning can be done with a simple dry cloth but if the oil has been used for too long a golden brown stain is left on metal portion of the sensor. In some cases it even comes out black and goo-ey which is basically old engine oil turned into sludge. if it's stained then you
CRANKSHAFT SENSOR (CKP)
This sensor is very similar to the cam position sensor in functionality. It is responsible for telling the ECM the exact location of the crankshaft as well as the RPM (rotations per minute) of the engine. With this information the ECM knows the position of each piston in each cylinder. Using the cam sensor readings as well as the Crank sensor readings the ECM knows exactly which injector needs to be activated. The synchronization of the cam shaft and the crank shaft in an engine is the key to engine performance. This synchronization is also referred to as the engine timing. With the correct timing you will get the fuel and spark delivered at the right time.
It is located at the bottom of the engine somewhere close to the crankshaft.
Cleaning technique for this sensor is exactly the same as the cam sensor. Cleaning once a year is good enough for this sensor.
Note - if your car does not start a possible reason could be a faulty crank sensor or a broken wire in the crank sensor circuit.
2SYSTEM COMPONENTS
Interior Lighting is controlled through four lighting circuits. Three circuits are BC1 controlled, the fourth, Ashtray Lighting, is controlled via the External Light Switch.
INTERIOR LIGHT SWITCH (ON/OFF MODE)
The interior light switch can be used to turn the interior lights ON and OFF. The interior light switch will operate at all times, except when the alarm is armed. If the interior light switch is used to turn on the interior light, the light stays on for 16 minutes, regardless of the state or change of state of the ignition switch. The interior light will fade off when the vehicle is externally locked, after this the interior light control will be in the "automatic" mode again
TRANSMISSION CONTROL UNIT
ABOUT
A Transmission control unit or TCU is a device that controls modern electronic automatic transmissions. A TCU generally uses sensors from the vehicle as well as data provided by the engine control unit (ECU) to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.
Electronic automatic transmissions have been shifting from purely hydro mechanical controls to electronic controls since the late 1980s. Since then, development has been iterative and today designs exist from several stages of electronic automatic transmission control development. Transmission solenoids are a key component to these control units.
The evolution of the modern automatic transmission and the integration of electronic controls have allowed great progress in recent years. The modern automatic transmission is now able to achieve better fuel economy, reduced engine emissions, greater shift system reliability, improved shift feel, improved shift speed and improved vehicle handling. The immense range of programmability offered by a TCU allows the modern automatic transmission to be used with appropriate transmission characteristics for each application.
On some applications, the TCU and the ECU are combined into a single unit as a power train control module (PCM
INPUT PARAMETERS
The typical modern TCU uses signals from engine sensors, automatic transmission sensors and from other electronic controllers to determine when and how to shift. More modern designs share inputs or obtain information from an input to the ECU, whereas older designs often have their own dedicated inputs and sensors on the engine components. Modern TCUs are so complex in their design and make calculations based on so many parameters that there are an indefinite amount of possible shift behaviours
TRANSMISSION FLUID TEMPERATURE SENSOR (TFT)
This may also be known as Transmission Oil Temperature. This sensor determines the fluid temperature inside the transmission. This is often used for diagnostic purposes to check ATF (Automatic Transmission Fluid) at the correct temperature. The main use of this has been as a failsafe feature to downshift the transmission if the ATF becomes extremely hot. On more modern TCUs this input allows the TCU to modify the line pressure and solenoid pressures according to the changing viscosity of the fluid based on temperature, and also to determine regulation of the torque converter lock-up clutch
KICK DOWN SWITCH
One of the most common inputs into a TCU is the kick down switch which is used to determine if the accelerator pedal has been depressed past full throttle. When activated the transmission downshifts into the lowest permissible gear based on current road speed to use the full power reserves of the engine. This is still present in most transmissions though is no longer as necessary to use as the TCU uses the throttle position sensor and rapid rate of change to determine whether a downshift may be necessary, thus there is no need to use the kick down feature in most circumstances
OUTPUTS TO OTHER CONTROLLERS
The TCU provides information about the health of the transmission, such as clutch wear indicators and shift pressures, and can raise trouble and set the malfunction indicator lamp on the instrument cluster if a serious problem is found. An output to the cruise control module is also often present to deactivate the cruise control if a neutral gear is selected, just like on a manual transmission.
COMPONENTS AND DESIGN
ESC incorporates yaw rate control into the anti-lock braking system (ABS). Yaw is a rotation around the vertical axis; i.e. spinning left or right. Anti-lock brakes enable ESC to brake individual wheels. Many ESC systems also incorporate a traction control system (TCS or ASR), which senses drive-wheel slip under acceleration and individually brakes the slipping wheel or wheels and/or reduces excess engine power until control is regained. However, ESC achieves a different purpose than ABS or Traction Control.
The ESC system uses several sensors to determine what the driver wants (input). Other sensors indicate the actual state of the vehicle (response). The control algorithm compares driver input to vehicle response and decides, when necessary, to apply brakes and/or reduce throttle by the amounts calculated through the state space (set of equations used to model the dynamics of the vehicle). The ESC controller can also receive data from an issue commands to other controllers on the vehicle such as an all wheel drive system or an active suspension system to improve vehicle stability and controllability.
The sensors used for ESC have to send data at all times in order to detect possible defects as soon as possible. They have to be resistant to possible forms of interference (rain, holes in the road, etc.). The most important sensors are: